the present would be our present. Just because DOFP could change the timeline, that doesnt mean the whole x-men world dissapears

"Our" present would not be anything like the present of the original trilogy. You can't make an X-Men sequel with Jackman, Berry, Page, Paquin, Ashmore, Grammer & Foster if the characters they play don't even know each other in the new "present".

The new present is not the present at the end of X3 or Days of Future Past. That's why it makes a sequel starring that ensemble highly unlikely and nonsensical.